Updated: 2022/Sep/29
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SYSLOGD(8) System Manager's Manual SYSLOGD(8)
NAME
syslogd - log systems messages
SYNOPSIS
syslogd [-nrSsTUvX] [-B buffer_length] [-b bind_address] [-d [[~]what]]
[-f config_file] [-g group] [-m mark_interval] [-o output_format]
[-P file_list] [-p log_socket [-p log_socket2 ...]]
[-t chroot_dir] [-u user]
DESCRIPTION
syslogd reads and logs messages to the system console, log files, other
machines and/or users as specified by its configuration file. The
options are as follows:
-B buffer_length
Sets the receiving buffer length. The default is 16384
bytes. If syslogd reports buffer overflow, this needs
increasing. If you don't care about it being reported,
see the -X option.
-b bind_address Specify one specific IP address or hostname to bind to.
If a hostname is specified, the IPv4 or IPv6 address
which corresponds to it is used.
-d [[~]what] Do not disassociate from the controlling terminal and
enable debugging to the standard output. The optional
what argument is a number that selects which categories
of the debug messages are to be enabled. A tilde (`~')
before what inverts its meaning so that all messages
except those selected by what are enabled.
-f config_file Specify the pathname of an alternative configuration
file; the default is /etc/syslog.conf.
-g group Set GID to group after the sockets and log files have
been opened.
-m mark_interval
Select the number of minutes between ``mark'' messages;
the default is 20 minutes.
-n Do not perform hostname lookups; report only numeric
addresses.
-o output_format
Select output message format.
bsd, rfc3164 traditional BSD Syslog format (default)
syslog, rfc5424 new syslog-protocol format
-P Specify the pathname of a file containing a list of
sockets to be created. The format of the file is simply
one socket per line.
-p log_socket Specify the pathname of a log socket. Multiple -p
options create multiple log sockets. If no -p arguments
are given, the default socket of /var/run/log is used.
-r Disable the compression of repeated instances of the
same line into a single line of the form "last message
repeated N times".
-S Sync kernel messages to disk immediately.
-s Select "secure" mode, in which syslogd does not listen
on a UDP socket but only communicates over a UNIX domain
socket. This is valuable when the machine on which
syslogd runs is subject to attack over the network and
it is desired that the machine be protected from
attempts to remotely fill logs and similar attacks.
-T Always use the local time and date for messages received
from the network, instead of the timestamp field
supplied in the message by the remote host. This is
useful if some of the originating hosts can't keep time
properly or are unable to generate a correct timestamp.
-t chroot_dir chroot(2) to chroot_dir after the sockets and log files
have been opened.
-U Unique priority logging. Only log messages at the
priority specified by the selector in the configuration
file. Without this option, messages at the specified
priority or higher are logged. This option changes the
default priority comparison from `>=' to `='.
-u user Set UID to user after the sockets and log files have
been opened.
-v Verbose logging. If specified once, the numeric
facility and priority are logged with each locally-
written message. If specified more than once, the names
of the facility and priority are logged with each
locally-written message.
-X Disable logging of buffer overflow.
syslogd reads its configuration file when it starts up and whenever it
receives a hangup signal. For information on the format of the
configuration file, see syslog.conf(5).
syslogd reads messages from the UNIX domain socket /var/run/log, from an
Internet domain socket specified in /etc/services, and from the special
device /dev/klog (to read kernel messages).
syslogd creates the file /var/run/syslogd.pid, and stores its process id
there. This can be used to kill or reconfigure syslogd.
By using multiple -p options, one can set up many chroot environments by
passing the pathname to the log socket (/var/run/log) in each chroot area
to syslogd. For example:
syslogd -p /var/run/log -p /web/var/run/log -p /ftp/var/run/log
Note: the normal log socket must now also be passed to syslogd.
The logged message includes the date, time, and hostname (or pathname of
the log socket). Commonly, the program name and the process id is
included.
The date and time are taken from the received message. If the format of
the timestamp field is incorrect, time obtained from the local host is
used instead. This can be overridden by the -T flag.
Accesses from UDP socket can be filtered by libwrap configuration files,
like /etc/hosts.deny. Specify "syslogd" in daemon_list portion of the
configuration files. Refer to hosts_access(5) for details.
SYSLOG PROTOCOL NOTES
syslogd accepts messages in traditional BSD Syslog or in newer Syslog
Protocol format. See RFC 3164 (BSD Syslog) and RFC 5424 (Syslog
Protocol) for detailed description of the message format. Messages from
the local kernel that are not tagged with a priority code receive the
default facility LOG_KERN and priority LOG_NOTICE. All other untagged
messages receive the default facility LOG_USER and priority LOG_NOTICE.
FILES
/etc/syslog.conf The configuration file.
/var/run/syslogd.pid The process id of current syslogd.
/var/run/log Name of the UNIX domain datagram log socket.
/dev/klog The kernel log device.
SEE ALSO
logger(1), syslog(3), services(5), syslog.conf(5), newsyslog(8)
The BSD syslog Protocol, RFC, 3164, August 2001.
The Syslog Protocol, RFC, 5424, March 2009.
HISTORY
The syslogd command appeared in 4.3BSD. Support for multiple log sockets
appeared in NetBSD 1.4. libwrap support appeared in NetBSD 1.6. Support
for RFC 5424, TLS encryption and authentication, signed messages appeared
in NetBSD 6.0.
NetBSD 10.99 November 8, 2022 NetBSD 10.99